\begin{table}[htbp]\centering
\def\sym#1{\ifmmode^{#1}\else\(^{#1}\)\fi}
\caption{Electoral System, Candidate Communication, and Change in Partisan Affect (Traits)\label{tab:apthetero}}
\begin{tabular}{l*{3}{c}}
\hline\hline
                &\multicolumn{1}{c}{(1)}   &\multicolumn{1}{c}{(2)}   &\multicolumn{1}{c}{(3)}   \\
                &Affective Polarization   & In-Group   &Out-Group   \\
                &     b/se   &     b/se   &     b/se   \\
\hline
RCV Compliment  &    0.006   &   -0.005   &   -0.017*  \\
                &  (0.005)   &  (0.008)   &  (0.008)   \\
RCV Comp. + Endorse&   -0.003   &   -0.011   &   -0.006   \\
                &  (0.005)   &  (0.008)   &  (0.008)   \\
Conservativism  &    0.016***&    0.008***&   -0.024***\\
                &  (0.001)   &  (0.001)   &  (0.001)   \\
RCV Compliment x Conservativism&   -0.001   &    0.003   &    0.004*  \\
                &  (0.001)   &  (0.002)   &  (0.002)   \\
RCV Comp. + Endorse x Conservativism&    0.001   &    0.003   &    0.002   \\
                &  (0.001)   &  (0.002)   &  (0.002)   \\
Constant        &   -0.076***&   -0.032***&    0.120***\\
                &  (0.004)   &  (0.006)   &  (0.006)   \\
\hline
R$^2$           &     0.32   &     0.07   &     0.29   \\
\textit{N}      &     2250   &     2250   &     2250   \\
\hline\hline
\end{tabular}
\end{table}
